1. Technical Field
The present disclosure relates to a catheter assembly, and in particular, to a hemodialysis catheter assembly adapted to facilitate bidirectional fluid flow.
2. Description of the Related Art
Catheters are flexible medical instruments for use in the introduction and withdrawal of fluids to and from body cavities, ducts, and vessels. Catheters have particular application in hemodialysis procedures, in which blood is withdrawn from a blood vessel for treatment and subsequently returned to the blood vessel for circulation through a patient's body.
Many hemodialysis catheters include multiple lumens, e.g., dual or triple-lumen catheters, with one lumen being dedicated to the withdrawal of fluid from a vessel via communication in one direction, and at least one other lumen being dedicated to the return of fluid to the vessel via communication in another direction. Generally, the lumen through which fluid is withdrawn is referred to as the “arterial” lumen, and the lumen through which fluid is returned is referred to as the “venous” lumen. Fluid enters the arterial lumen and exits the venous lumen through corresponding openings in the catheter wall. During an exemplary hemodialysis procedure, after placement of a multiple lumen catheter, blood is withdrawn from the patient through the arterial lumen of the catheter, and is directed to a hemodialysis unit for dialysis, or purification, to remove waste and toxins. The dialyzed blood is then returned to the patient through the venous lumen of the catheter.
Known hemodialysis catheters incorporate various catheter tip designs. For example, a catheter may include a design with staggered venous and arterial lumens, and thus, staggered venous and arterial openings. The staggered openings ensure blood returning to the patient will be expelled from the venous lumen downstream of the arterial opening. However, poor flow performance often occurs due to occlusion in the arterial lumen of the catheter resulting from, e.g., positional occlusion, or the formation of a fibrin sheath or thrombus.
Current measures taken to resolve flow occlusion include repositioning the patient, flushing the lumens of the catheter, and reversing the blood lines of the catheter to the hemodialysis unit. However, these measures create a situation wherein cleaned blood is expelled upstream relative to the catheter inlet, which may undesirably increase the potential for clean blood being drawn back into the catheter. This “recirculation” of the blood results in inefficient dialysis by increasing treatment time to reach prescribed blood cleanliness levels.
Several factors pertaining to the venous and arterial openings in the wall of a catheter have been found to impact the likelihood of occlusion and recirculation during a hemodialysis procedure. These factors include, for example, the circumferential and axial distances between the openings, and the perimeter and circumferential heights thereof. Known catheter tip designs, however, are deficient in the optimization of one or more of these factors. For example, U.S. Pat. Nos. 5,403,291 and 5,489,278, each to Abrahamson, disclose a catheter assembly including a body portion defining longitudinally spaced intake and return lumens in respective fluid communication with a side opening formed in a wall of the body portion and an opening formed at the distal tip. The side opening is defined by two pairs of generally parallel wall portions, and the opening at the distal tip is substantially circular in configuration.
Additional examples of known catheter tip designs are disclosed in U.S. Pat. Nos. 5,685,867 and 5,961,486, each to Twardowski, et al, which disclose a catheter including internal venous and arterial lumens. The venous and arterial lumens are in communication with corresponding openings positioned at the distal end of the catheter that are spaced longitudinally from each other.
Given the desirability of reducing the likelihood of occlusion and limiting recirculation, a catheter tip design including structure that optimizes one or more of the factors identified above would be advantageous.